The present disclosure relates to a device for measuring the torque, the direction of rotation and the speed of rotation of a shaft of a transmission, in particular an output shaft of an azimuth transmission of a wind power plant, in which bands can be mounted in a fixed position on an outer circumference of the shaft, which bands can be detected by measuring sensors and allow torsion of the shaft to be measured, wherein the measuring sensors each have a Hall effect sensor. The disclosure furthermore relates to a method for operating a device of this kind.
The area of application of the present disclosure extends particularly to azimuth transmissions for modern wind power plants. The area of application is not restricted to wind power plants, there being the possibility on many types of crane, for example, to rotate the boom about a vertical axis by means of a plurality of transmissions.
It is known from the general prior art that the nacelle on wind power plants is rotated in order to adjust the rotor to the wind direction. The rotor blades must also be rotated about the longitudinal axis thereof in order to set the correct blade position. In this case, very high frictional torques have to be overcome in the respective pitch and azimuth bearings.
Owing to the high torques required, hydraulic drives or electric drives can be used. In the case of the hydraulic drive, a hydraulic cylinder engages on an eccentric, for example, and thereby allows rotation. Here, however, the rotary movement is restricted to less than half a revolution. If larger rotary movements are to be carried out or if the use of a hydraulic solution is not desired for other reasons, an electric drive is used. In the case of electric drives, the high rotational speed of an electric motor is converted to a low rotational speed by means of a multi-stage transmission. The output pinion of the transmission engages in a gear ring, which is generally embodied as part of the bearing. The nacelle of the wind power plant can thereby be rotated.
If the required torques are very high, a plurality of drives is fitted. Defects, e.g. faulty bearings, can occur in the transmissions of the drives, causing a rise in the frictional torque in the transmission. As a result, the transmission outputs less torque to the gear ring for the same motor power.
If there is only a small number of drives, the motor power must increase in order to achieve the same drive torque. At the same time, the motor current also rises. By means of the rise in the current, which can be measured, it is possible to detect a fault in the transmission. If there is a very large number of drives, the rise in the motor current is so small that unambiguous measurement is not possible and therefore a fault cannot be detected. If the entire drive torque of the electric motor is lost in overcoming the friction in the faulty bearing, the output shaft of the transmission no longer drives the gear ring; instead, the output shaft is driven by the gear ring. Owing to the fault, the remaining drives and the transmissions thereof are overloaded and, in the long term, are likewise damaged.
DE 10 2006 054 179 A1 discloses a device for measuring the torque on a shaft, in particular for measuring the steering torque in a power-assisted rack and pinion steering system in a motor vehicle. The shaft is divided into an input shaft and an output shaft, with the two shaft parts being connected by a torsion element of reduced stiffness. The torsion element carries a magnetic transmitter unit, the coding of which can be modified by torsion and can be read out by a sensor unit assigned to the transmitter unit. However, a device of this kind for measuring the torque on a shaft is not suitable for torques of high magnitude of the kind that occur in azimuth transmissions of a wind power plant.
DE 199 07 270 A1 discloses a different device for measuring the torque on a shaft, in particular the output shaft of a motor vehicle transmission. Over a predetermined axial range, the shaft is provided with just one sleeve, which is connected to the shaft in such a way that torsion of the shaft leads to torsion of the sleeve. The sleeve is assigned a measuring arrangement for determining the magnitude of the torsion. Although measurement of the torque on a shaft can be achieved with this technical solution, it is a disadvantage of the known solution that only shafts of relatively small diameter, which exhibit a large amount of torsion within a relatively small shaft segment, can be measured. This device does not offer the possibility of precise measurement for small amounts of torsion.